Analyse comparée des effets de dragage et de chasse hydraulique sur l'envasement à l'amont du bassin maritime de la Rance

Comparative study of dredging and flushing effects on sedimentation in the upper part of the Rance estuary

Laboratoire de Géomorphologie E.P.H.E. URA 904 du CNRS " Dynamique et gestion des espaces littoraux " 15 boulevard de la mer, 35800 Dinard

Abstract

Since a few years, an exceptional muddy sedimentation increase was observed in the upper part of the Rance estuary, and a dredging of the navigation channel was required. But the dredged sediments were transported at a short distance only because ebb current is too weak to allow the discharge of suspended load in the lower part of the maritime basin. The excess of fine particles deposition is linked to drought and a low river inflow during three years in a row. A fluvial basin located at the upper part of the marine stretch of the estuary can be used for hydraulic flushing which happens to be more efficient for fluid mud resuspension and translation of the turbidity maximum towards the outer part of the Rance estuary.